276 PROCEEDINGS OF SOCIETIES. 



Against this custom, too prevalent now-a-days, I must enter my protest : 

 every distinct set of forms possessing one or two important parallel cha- 

 racters in common, should rather constitute a genus, than by, as is too 

 often done, grouping a number of these in one genus, necessitate the 

 formation of sub-groups, which are always most puzzling to the student, 

 and of no use unless to the systematist addicted to mere number of fami- 

 lies in some preconceived order of numeral arrangement. 



List of British Species of Oniscoidea. 



Family.— AEMADILLID^. 



Genus. — Aemadillium (Brandt). 



(Armadillidium of Brandt shortened in conformity to modern usage.) 

 Armadillium vulgare (Latr. sp.) 



Synonyms : Oniscus armadillo (Linn.), 0. cinereus (Zenh.), Arma- 

 dillo vulgaris (Latr.), A. variegatus (ib.), Armadillidium Zenckeri (Br.), 

 Armadillo opacus, variegatus, Willii (Schceffer). 



Body smooth, elliptical ; median plate arched above, scarcely sur- 

 passing frontal line. Terminal ring of abdomen narrow (coxae obsolete), 

 triangular : apex truncate. False feet of last pair : basis nearly com- 

 pletely concealed, bilobed ; internal lobe much shorter than external ; 

 a raised transverse ridge on inferior face. Ischium flattened, somewhat 

 triangular, wider betow than above. Secondary appendage trigonal, 

 broader below than above, compressed, hairy at the end. Second joint 

 of external antennae lobed. 



Colour: dark steel-gray, almost black; steel-gray blotched with 

 patches and spots of whitish-yellow and red browns. 



Habit : rolls itself into a ball. 



Habitat : dry places under stones, decaying timber, and amidst 

 herbage. 



Distribution : Ireland generally. England — London, Kent. 



Family.— ONISCID^E. 



Genus. — Oniscus (Linn.). 

 1. — Oniscus murarius (Cuvier). 



Synonyms : 0. asellus (Linnceus, and Auct.). 



Body oval, shining, covered with smooth granules ; lateral lobes of 

 head large, inclined backwards; frontal line somewhat emarginate ; ter- 

 minal ring of abdomen elongate, triangular, convex above ; coxae ter- 

 minating as acute angle ; coxae of fifth concealing origin of accessory 

 appendage. Accessory appendage nearly equalling ischium in length. 

 Second joint of external antennae lobed internally. 



